The present invention relates to analytical instruments and particularly to an inert gas fusion analyzer for simultaneously determining hydrogen, oxygen, and nitrogen.
In inert gas fusion instruments, it is typical to fuse a sample in an electrode furnace utilizing a carrier gas sweeping the byproducts of fusion through a variety of detectors, either infrared detectors or thermal conductivity cells, to determine the concentration of elements such as hydrogen, oxygen, and nitrogen. When thermal conductivity cells are employed, helium and hydrogen fall within one group of elements having particular thermal characteristics while nitrogen, argon, carbon dioxide, and water have significantly different thermal characteristics. As a result, in instruments employing thermal conductivity cells for the detection of elements, it is typical to use a carrier gas from one group, such as helium, to detect a specimen gas from another group, such as nitrogen or oxygen. Alternatively, when using thermal conductivity cells for detecting hydrogen, a heavier gas, such as nitrogen or argon, is employed so that the thermal conductivity cell can distinguish between the specimen gas and the carrier gas. As a result, the design of instruments for measuring hydrogen have resulted in a separate instrument from those instruments used to detect nitrogen and oxygen.
Although attempts have been made to, in effect, incorporate two instruments in one cabinet utilizing separate flow paths and requiring two separate samples to be run, there remains a need for a single path instrument which can measure hydrogen, oxygen, and nitrogen from a single sample and provide high accuracy for low concentration samples.
The present invention solves this need by the utilization of multiple infrared sensors, a catalytic converter, a scrubber and a thermal conductivity cell all coupled in a series flow path from an electrode furnace to provide a single pass (i.e., one sample) analyzer which allows for fast analysis, allows for the speciation of all analytes, including hydrogen samples, requires no purging of carrier gas between different sample types, utilizes a single carrier gas, and eliminates the molecular sieve chromatographic column and Shutze converters of prior art systems. The resultant analyzer, therefore, provides improved quicker results with less plumbing (i.e., gas conduits and valving) than prior art systems and does so in a single instrument.
These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.